JPH11350946A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the exhaust emission control catalytic device capable of surely maintaining the function of the exhaust emission control catalyst (NOx catalyst) even with the adhesion of the substances other than the nitrogen oxides (NOx) which affect the emission control performance. SOLUTION: This device is provided with an adhesion-quantity estimation means whereby the quantity of adhesion to an exhaust emission control catalyst of the substances affecting exhaust emission control performance is detected. It is also provided with catalyst heating means (S24, 26, 28) whereby the temperature of the exhaust emission control catalyst is raised when the quantity of adhesion estimated by the adhesion-quantity estimation means has reached a predetermined level (S12). Further, the adhesion-quantity estimation means incorporates a fuel consumption calculation means (S10) which sums the fuel consumption during the operation of internal combustion engine on lean combustion, and the adhesion of the substance affecting the emission control performance is presumed to have reached predetermined adhesion quantity when the amount of fuel consumption calculated by the fuel consumption calculation means has reached a predetermined value (S12).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst device for purifying exhaust gas of an internal combustion engine, and more particularly to a device having a function of recovering purification efficiency.

[0002]

2. Related Art When the internal combustion engine is in a predetermined operating state, the air-fuel ratio is controlled to a target value (e.g., 22) leaner than the stoichiometric air-fuel ratio (14.7).
2. Description of the Related Art There is known an air-fuel ratio control method for improving the fuel efficiency and the like of an engine. In such a lean air-fuel ratio control method,
In a conventional three-way catalyst device, nitrogen oxides (NO
x) cannot be sufficiently purified.

In order to solve this problem, NOx in exhaust gas is adsorbed in an oxygen-rich state (oxidizing atmosphere),
An exhaust purification catalyst having a characteristic of reducing adsorbed NOx in a hydrocarbon (HC) excess state (reducing atmosphere), so-called NO
It is known to use x catalysts to reduce NOx emissions to the atmosphere. In this NOx catalyst, NOx is adsorbed during lean air-fuel ratio control. However, if the lean combustion operation is continuously performed, the amount of catalyst adsorbed is limited. Most of the NOx will be released to the atmosphere. So, NOx
A method in which the air-fuel ratio is switched to a rich air-fuel ratio control for controlling the air-fuel ratio to a stoichiometric air-fuel ratio or a value close to the stoichiometric air-fuel ratio before the catalyst adsorption amount reaches saturation and NOx is reduced in a reducing atmosphere (rich state) is disclosed in It is known from JP-A-5-133260.

In this air-fuel ratio control method, the timing of switching from the lean combustion operation to the rich combustion operation is controlled based on the elapsed time from the start of the lean air-fuel ratio control. After switching to the control, the NO adsorbed on the catalyst by the rich air-fuel ratio control
When the reduction of x is completed, the air-fuel ratio control is returned to the lean air-fuel ratio control again. Thus, by alternately repeating the lean combustion operation and the rich combustion operation, the adsorption capacity of the NOx catalyst is maintained, and the NOx amount is reduced. Like that.

[0005]

The substance adsorbed on the NOx catalyst only needs to be NOx, but actually, substances other than NOx, for example, sulfur and its compounds also adhere thereto. Such a substance other than NOx (hereinafter referred to as a purification ability reducing substance) is used in a place where NOx is to be adsorbed.
Instead, NOx is adsorbed instead, and as a result, the NOx adsorption capacity is reduced.

As described above, NOx adhering to the NOx catalyst
The other purification performance reducing substances cannot be removed even by performing the air-fuel ratio control as disclosed in the above-mentioned publication, and the amount of the deposited substances increases with the passage of time. If the accumulation of such a purification-reducing substance is left as it is, the NOx adsorbing ability will only decrease, and the NOx catalyst may not fulfill its function sufficiently.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an exhaust gas purifying catalyst (NO) even if a substance having a low purifying ability other than nitrogen oxide (NOx) adheres. An object of the present invention is to provide an exhaust gas purifying catalyst device capable of reliably maintaining the function of a NOx catalyst.

[0008]

According to one aspect of the present invention, an exhaust system is provided in an exhaust passage of an internal combustion engine and adsorbs nitrogen oxides in exhaust gas during a lean combustion operation. In an exhaust gas purifying catalyst device for an internal combustion engine equipped with a purifying catalyst, an adhering amount estimating means for estimating an adhering amount of the purifying ability reducing substance adhering to the exhaust purifying catalyst;
Catalyst heating means for raising the temperature of the exhaust gas purification catalyst when the amount of adhesion estimated by the amount of adhesion estimation means has reached a predetermined amount of adhesion, wherein the amount of adhesion estimation means comprises the lean combustion of the internal combustion engine. A fuel consumption amount accumulating means for accumulating a fuel consumption amount during operation; and when the fuel consumption amount integrated value obtained by the fuel consumption amount accumulating means reaches a predetermined value, the adhesion amount of the purification-capacity reducing substance is reduced to the predetermined value. It is characterized in that it is estimated that the amount of adhesion has been reached.

Thus, the amount of the substance having reduced purification ability adsorbed on the exhaust gas purification catalyst and reducing the purification ability of nitrogen oxides is estimated by the attached amount estimating means, and when the attached amount exceeds the predetermined amount, The temperature of the exhaust purification catalyst is raised by the catalyst heating means, the substance having reduced purification ability is favorably burned and removed from the exhaust purification catalyst, and the ability of adsorbing nitrogen oxides to the exhaust purification catalyst is restored. ,
When estimating the adhering amount of the purifying ability reducing substance by the adhering amount estimating means, the fuel consumption amount accumulating means accumulates the fuel consumption amount of the internal combustion engine during the lean combustion operation in which the purifying ability decreasing substance easily adheres and the catalyst is greatly deteriorated. In addition, the amount of the substance having reduced purification ability is easily and accurately estimated based on the integrated value of the consumed fuel amount.

According to a second aspect of the present invention, there is provided an exhaust purification catalyst device for an internal combustion engine, the exhaust purification catalyst device being provided in an exhaust passage of the internal combustion engine and adsorbing nitrogen oxides in exhaust gas during a lean combustion operation. An adhesion amount estimating means for estimating an adhesion amount of the purification performance reducing substance adhering to the exhaust gas purification catalyst; and, when the adhesion amount estimated by the adhesion amount estimating means reaches a predetermined adhesion amount, the temperature of the exhaust gas purification catalyst. A catalyst heating means for raising the temperature of the exhaust gas purifying catalyst, and a catalyst temperature detecting means for detecting a temperature of the exhaust gas purification catalyst; and a case wherein the temperature detected by the catalyst temperature detecting means is equal to or lower than a predetermined temperature. A fuel consumption amount integrating means for integrating the consumed fuel amount of the purified fuel amount. Chakuryou is characterized in that estimated to have reached the predetermined deposition amount.

[0011] With this, the amount of the purifying ability reducing substance adsorbed on the exhaust gas purifying catalyst and reducing the purifying ability of nitrogen oxides is estimated by the adhering amount estimating means, and when the adhering amount exceeds a predetermined adhering amount, The temperature of the exhaust purification catalyst is raised by the catalyst heating means, the substance having reduced purification ability is favorably burned and removed from the exhaust purification catalyst, and the ability of adsorbing nitrogen oxides to the exhaust purification catalyst is restored. ,
When estimating the adhering amount of the purifying ability reducing substance by the adhering amount estimating means, the consumed fuel amount is accumulated by the consumed fuel amount accumulating means when the purifying ability lowering substance whose catalyst temperature is equal to or lower than a predetermined temperature is likely to adhere, thereby purifying. The attached amount of the performance reducing substance is easily and accurately estimated based on the integrated value of the consumed fuel amount.

Further, in the invention according to claim 3, the internal combustion engine includes a fuel injection valve driven by a pulsed current, and the fuel consumption amount integrating means integrates a driving pulse width of the fuel injection valve, The integrated value is used as the integrated value of the consumed fuel amount. Thus, the amount of the substance having reduced purification ability is easily estimated from the integrated value of the drive pulse width of the fuel injection valve.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing an internal combustion engine provided with an exhaust purification catalyst device according to the present invention.
In the figure, reference numeral 1 denotes an automobile engine, for example, V
This is a type 6 cylinder gasoline engine body, and the combustion chamber, intake system, ignition system, etc. are designed to be able to perform lean combustion. In this V-type 6-cylinder gasoline engine main body (hereinafter simply referred to as engine main body) 1, three cylinders are arranged in one (left) bank 1a and the other (right) bank 1b, respectively. An air cleaner 5 and an air flow for detecting an intake air amount Af are provided to intake ports 2a and 2b provided for each cylinder of the left bank 1a and the right bank 1b via an intake manifold 4 to which fuel injection valves 3a and 3b are attached. An intake pipe 9 having a sensor 6, a throttle valve 7, an ISC (idle speed control) valve 8, and the like is connected.

As the air flow sensor 6, a Karman vortex air flow sensor or the like is preferably used. The ISC valve 8 is for controlling the idling speed, and is used to control the engine load L due to the operation of an air conditioner (not shown).
The function of adjusting the valve opening in accordance with the fluctuation of e changes the intake air amount and stabilizes the idling operation. In addition, the ISC valve 8 operates on the valve opening side during the air-fuel ratio correction control described later, and acts so as to compensate for the output decrease due to the execution of the air-fuel ratio correction.

The exhaust ports 10a, 10b of each cylinder
The exhaust manifold 11a, through 11b, the air-fuel ratio sensor exhaust pipe 14 attached with (linear O ₂ sensor) 12 for detecting the air-fuel ratio is connected to the exhaust pipe 14, an exhaust purification A muffler (not shown) is connected via the catalyst 13. The exhaust purification catalyst 13 is N
It has two catalysts, an Ox catalyst 13a and a three-way catalyst 13b, and the NOx catalyst 13a is disposed upstream of the three-way catalyst 13b. The NOx catalyst 13a adsorbs NOx (nitrogen oxide) in an oxidizing atmosphere and
In the presence of reducing atmosphere (hydrocarbon), and NOx N ₂
(Nitrogen) or the like. NOx
As the catalyst 13a, for example, Pt having heat deterioration resistance is used.
And a catalyst comprising an alkali rare earth such as lanthanum and cerium. A catalyst temperature sensor (catalyst temperature detecting means) 26 is connected to the NOx catalyst 13a.
The temperature of the x catalyst 13a can be detected up to a high temperature range. Note that the catalyst temperature sensor 26 can also function as an exhaust gas temperature estimating unit that estimates the temperature of the exhaust gas from the engine body 1.

On the other hand, the three-way catalyst 13b has a function of oxidizing HC and CO (carbon monoxide) and reducing NOx. The reduction of NOx by the three-way catalyst 13b is based on the stoichiometric air-fuel ratio (14.7). ) Is maximized during combustion in the vicinity. In the engine body 1, ignition plugs 16a and 16b for igniting a mixed gas of air and fuel supplied to the combustion chambers 15a and 15b from the intake ports 2a and 2b are arranged for each cylinder.
Reference numeral 18 denotes a crank angle sensor for detecting a crank angle synchronizing signal θCR from an encoder linked to the camshaft, reference numeral 19 denotes a throttle sensor for detecting the opening θTH of the throttle valve 7, and reference numeral 20 denotes a cooling water temperature TW. Reference numeral 21 denotes an atmospheric pressure sensor that detects the atmospheric pressure Pa, and reference numeral 22 denotes an intake air temperature sensor that detects the intake air temperature Ta.

The engine speed (engine speed)
Ne is calculated from the generation time interval of the crank angle synchronization signal θCR detected by the crank angle sensor 18. The volume efficiency ηv is calculated from the air flow rate Af detected by the air flow sensor 6 and the engine rotation speed Ne and the like, and the atmospheric pressure Pa detected by the atmospheric pressure sensor 21 and the intake air temperature detected by the intake air temperature sensor 22 are calculated. It is corrected by Ta or the like. Further, the engine load Le is determined by the throttle sensor 1
9 is calculated from the throttle opening θTH detected by the control unit 9 and the volume efficiency ηv.

An input / output device (not shown) and a storage device (ROM, RA,
M, a non-volatile RAM, etc.), a central processing unit (CPU), and an ECU including a timer counter functioning as a timer.
(Electronic control unit) 23 is provided to perform air-fuel ratio control of the engine body 1, ignition timing control, intake air amount control, refresh control of an exhaust purification catalyst device described later, and the like. On the input side of the ECU 23, there is provided a distance meter 25 for counting the traveling distance of the vehicle by the integrated value of the vehicle speed pulse and the like.
And various sensors described above are connected, and detection information from these sensors is input. On the other hand, the fuel injection valves 3a and 3b, the ignition unit 24, and a hydraulic controller 60 of the automatic transmission 30, which will be described later, are connected to the output side, and calculations are performed for these based on input information from various sensors. The optimal value is output. The fuel injection valves 3a and 3b are controlled by a command from the ECU 23.
Driving is performed by supplying a pulsed current, and the fuel injection amount is determined by the pulse width of the current. The ignition unit 24 outputs a high voltage to the ignition plugs 16a and 16b of each cylinder according to a command from the ECU 23.

FIG. 2 shows a schematic configuration of a power plant of a vehicle equipped with an engine body 1 having the above-mentioned exhaust gas purifying catalyst device and an automatic transmission (AT) 30. As shown in the figure, the automatic transmission 30 is connected to an output shaft 31 of the engine body 1, and a drive shaft (not shown) is connected to a drive shaft 50 of the automatic transmission 30 via a differential gear or the like. I have.

The automatic transmission 30 comprises an automatic transmission main body 32 and a torque converter 33. The automatic transmission main body 32 incorporates hydraulic friction engagement elements such as a hydraulic clutch and a hydraulic brake in addition to a plurality of sets of planetary gears, but the description thereof is omitted here. Torque converter 33
Is a fluid coupling, and a housing 33, a casing 34,
It comprises a pump 36, a turbine 37, a stator 38 and the like. The casing 34 is connected to the output shaft 31 and rotates in synchronization with the output shaft 31.
The turbine 37 is connected to the input shaft 3 of the automatic transmission main body 32.
9, and the stator 38 is attached to the housing 33 via a one-way clutch (not shown).

The casing 34 is filled with hydraulic oil. This hydraulic oil is discharged by a pump 36 that rotates together with the output shaft 31 to rotate a turbine 37. As a result, the torque converter 33 functions as a fluid coupling, and the output of the engine body 1 is transmitted to drive wheels (not shown) via the automatic transmission body 32.

Between the casing 34 and the turbine 37,
The damper clutch 40 of a wet single plate type is interposed, and the output shaft 31
And the input shaft 39 can be directly connected. In the directly connected state in which the damper clutch 40 is engaged, the output from the output shaft 31 is directly transmitted to the input shaft 39 without using the hydraulic oil. In this case, the torque converter 33 does not function as a fluid coupling. Will be.

An oil passage 42 extends between the turbine 37 of the casing 34 and the damper clutch 40, and an oil passage 46 extends between the casing 34 and the damper clutch 40. The oil passage 42 and the oil passage 46 are connected to a control valve (not shown) in the hydraulic controller 60. The control valve is connected to a hydraulic source (not shown) for supplying hydraulic oil of a predetermined pressure. The hydraulic oil supplied from the hydraulic pressure source circulates through an oil passage 42 and an oil passage 46 via a control valve. The duty of the control valve is controlled in accordance with an output signal of the ECU 23, so that The circulation direction can be switched.

When the circulation direction is the direction from the oil passage 46 to the oil passage 42, the hydraulic oil from the hydraulic pressure source is supplied between the casing 34 and the damper clutch 40 through the oil passage 46, Is discharged from the oil passage 42 between the turbine 37 and the damper clutch 40. As a result, the pressure between the casing 34 and the damper clutch 40 increases, and the damper clutch 40 is pressed to the side where the engagement is released, and becomes in a non-direct connection state. In this non-direct connection state, the torque converter 33 functions as a normal fluid coupling.

Conversely, when the circulation direction is from the oil passage 42 to the oil passage 46, the hydraulic oil from the hydraulic source is supplied between the turbine 37 and the damper clutch 40 through the oil passage 42. Meanwhile, the casing 34 and the damper clutch 40
The intervening hydraulic oil is discharged from the oil passage 46. As a result, the pressure of the hydraulic oil between the turbine 37 and the damper clutch 40 increases, and the damper clutch 40 is pressed and engaged to be in a directly connected state. In such a directly connected state, the output of the output shaft 31 is directly transmitted to the input shaft 39 of the automatic transmission main body 32.

Next, the operation of the exhaust gas purifying catalyst device configured as described above will be described with reference to FIGS. 3 and 4 show a refresh control procedure executed by the ECU 23. This refresh control is performed when it is determined that deposits (purification-reducing substances) other than NOx that adhere to the NOx catalyst 13a, such as sulfur and its compounds, have reached a predetermined amount.
a, fuel and air are supplied to burn this fuel, and NO
A refresh operation (catalyst heating means) for heating the x catalyst 13a to a high temperature state is carried out,
This is to remove Ox so as not to be an obstacle when adsorbing on the NOx catalyst 13a.

First, in step S10, the ECU 23
Since the amount of the substance having reduced purification ability increases substantially in proportion to the integrated fuel consumption F of the engine body 1, the pulse widths of the currents driving the fuel injection valves 3a and 3b are integrated and calculated. In this way, the integrated fuel consumption F is obtained (fuel consumption integrating means), and based on the fuel consumption integrated amount F, the amount of the purification capability lowering substance adhering and accumulating on the NOx catalyst 13a is estimated (adhesion amount estimating means). .

The accumulated fuel consumption F may be calculated by integrating all the pulse widths of the drive current supplied to the fuel injection valve 3. However, the substance having a reduced purification ability adhered to the NOx catalyst 13a. However, since the number tends to increase in the case of the lean combustion operation, it is preferable to perform the integration only when the lean combustion operation is performed. Further, even when the temperature of the NOx catalyst 13a is equal to or lower than the predetermined temperature, the substance having a low purification ability easily adheres.
If the pulse width is integrated only when the temperature is equal to or lower than a predetermined temperature, the amount of the substance having reduced purification ability can be more appropriately estimated.

Next, in step S12, it is determined whether or not the amount of the substance having reduced purification ability has reached a predetermined amount based on whether or not the integrated fuel consumption amount F calculated in step S10 is equal to or more than a predetermined value F1. The predetermined value F1 is set to an appropriate value by an experiment or the like. The predetermined value F1 is in a range where the amount of the substance having a reduced purification ability does not exceed an allowable amount, that is, the amount of NOx emission that increases due to the adhesion of the substance having a reduced purification ability is a regulated value such as a law. Is set to a value that does not exceed. If the determination result is Yes (Yes),
It can be determined that the purifying ability reducing substance has exceeded the predetermined amount, and the process proceeds to step S16. On the other hand, when the result of the determination is No (No) and the integrated fuel consumption amount F has not reached the predetermined value F1, the process proceeds to step S14.

Step S14 is a step for judging whether or not the battery serving as the control power source has been once disconnected for maintenance of the vehicle or the like and has just been connected again. This determination is made when the battery is removed from the RAM of the ECU 23.
The estimated value of the adhered amount of the purification-reducing substance estimated based on the accumulated fuel consumption F stored in the vehicle or the travel distance D described later is temporarily reset to zero, and the estimated value of the adhered amount and the actual amount of adhered amount This is performed in order to prevent inconsistency with the data.

If the result of the determination in step S14 is No (No), the battery is connected, but the result of the determination of the accumulated fuel consumption F in step S12 has not yet reached the predetermined value F1. The determination can be made, and in this case, the routine ends without doing anything. On the other hand, if the determination result is Ye
If s (affirmative), immediately after the battery reconnection, the process proceeds to step S16, similarly to the determination result of Yes (affirmative) in step S12. Even if the battery is removed, EC
The integrated fuel consumption F
If the values such as the travel distance D and the like are reliably stored and held, the determination in step S14 may not be performed.

In step S16, it is determined whether or not the operating state of the engine body 1 is in a state in which the refresh operation can be performed, based on signal values from various sensors as operating state detecting means. Here, the volumetric efficiency ηv and the cooling water temperature TW, which are the calculation elements of the engine rotation speed Ne and the engine load Le, are to be determined, and whether the respective values fall within the inequalities shown in the following (1) to (3) It is determined whether or not it is.

Ne1 ≦ Ne ≦ Ne2 (1) ηv1 ≦ ηv ≦ ηv2 (2) TW1 ≦ TW (3) where Ne1, Ne2, ηv1, ηv2 and TW1 indicate thresholds, for example, Ne1 is 1500 rpm , Ne2 is 5000r
pm and ηv1 are 30%, ηv2 is 85%, and TW1 is set to, for example, 50 ° C. at which the warm-up operation can be considered completed. These thresholds indicate values in which the operating state of the engine body 1 changes from a so-called medium load range to a high load range. In this case, the exhaust temperature of the engine body 1 is equal to or higher than a predetermined temperature TEX (for example, 600 ° C.). It is estimated that there is.

As described above, the medium-high load operating state in which the operating state of the engine body 1 is changed from the medium load area to the high load area is used as a condition for establishing the refresh operation.
If the refresh operation is performed in a low load range smaller than Ne1, ηv1, the output of the engine body 1 is not stabilized, and the driving feeling may be deteriorated.
Further, in a high load region where the values of Ne and ηv are larger than Ne2 and ηv2, the exhaust gas temperature is high.
Since the Ox catalyst 13a is also in a high temperature state, if the refresh operation is performed in this state, the NOx catalyst 13a
This is because a may be overheated and burn out.

If the result of the determination in step S16 is No (No), that is, if any of Ne, ηv, and TW is out of the above range, it can be determined that the refresh operation should not be performed. Does not perform the refresh operation, and goes to step S16 again after step S18.
And the execution of step S16 is repeated until the result of the determination is no longer No (negative). In step S18, a flag f (RF) described later is reset to a zero value.

On the other hand, if the decision result in the step S16 is Yes.
(Affirmative), all values of Ne, ηv, TW are equal to the above inequality
When the operating state of the engine body 1 is within the range of (1) to (3), the operating state of the engine body 1 is in the middle load range to the high load range and the refresh operation can be performed. Proceed to step S20. At this time, the timer counter of the ECU 23 starts accumulating the elapsed time t.

In step S20, the flag f (R) for storing that the later-described refresh mode operation has been executed is stored.
This is a step of determining whether or not F) is the value 1. Immediately after the determination result of step S16 is Yes (Yes) and the refresh operation is enabled, the flag f (RF)
Is a reset zero value state (f (RF) = 0), in this case, the determination result in step S20 is necessarily No (negative), and the process proceeds to step S22.

Step S22 is a step for releasing the direct connection of the AT (automatic transmission). Here, the duty of the control valve of the hydraulic controller 60 is controlled.
The engagement of the damper clutch 40 of the automatic transmission 30 is released to bring it into a non-direct connection state. Thereby, the torque converter 33
Will function as a normal fluid coupling. By releasing the direct connection of the damper clutch 40 in this manner, the output fluctuation of the engine body 1 caused by the execution of the refresh operation described later is not directly transmitted to the automatic transmission 30, and the driving feeling is deteriorated. Can be prevented.
At the time of execution of step S22, the damper clutch 4
If 0 is already in the non-direct connection state, the non-direct connection state will be continued.

The following step S24 is a step for executing the refresh operation. Steps S24 to S28 constitute a temperature rising mode operation in the refreshing operation. Here, the temperature TCAT of the NOx catalyst 13a is set to a predetermined temperature T1 ( For example, 650
℃).

First, in step S24, air-fuel ratio correction control is performed for each cylinder. This air-fuel ratio correction is performed for a part of the cylinders of the engine body 1 (for example, # 1, # 3, and # 5 cylinders) in the lean combustion operation with a high air-fuel ratio and a large amount of air, while the remaining cylinders (for example, , # 2, # 4, and # 6 cylinders) are controlled to perform rich combustion operation with a low air-fuel ratio and a large amount of fuel.

The air-fuel ratio correction method for the lean combustion operation and the rich combustion operation is as follows.
The fuel amount is reduced under the constant air amount, while the air amount is reduced under the constant fuel amount on the rich combustion operation side. Specifically, the air-fuel ratio is corrected based on the following equation (4) for the lean combustion operation, and the air-fuel ratio is corrected based on the following equation (5) for the rich combustion operation.

LAF = AVAF + AVAF × DAF / 100 (4) RAF = AVAF−AVAF × DAF / 100 (5) where, LAF indicates a lean air-fuel ratio, RAF indicates a rich air-fuel ratio, and DAF indicates an air-fuel ratio correction. Indicates the amount (%). Also,
AVAF indicates an average air-fuel ratio between a lean air-fuel ratio and a rich air-fuel ratio, and is set here to, for example, a value of 14.7 which is a stoichiometric air-fuel ratio. The air-fuel ratio correction amount DAF (%) is set using a map (not shown) stored in advance based on the engine speed Ne and the volumetric efficiency ηv detected at the start of the refresh operation.

As described above, when the cylinders of the engine body 1 are operated at different air-fuel ratios at the same time, such as performing the lean combustion operation on some of the cylinders and performing the rich combustion operation on the remaining cylinders,
The exhaust gas discharged from the engine body 1 includes air discharged from the cylinders that have performed the lean combustion operation, that is, exhaust gas containing residual oxygen, and unburned hydrocarbons (unburned hydrocarbons) that have been discharged from the cylinders that have performed the rich combustion operation. Combustion HC) and exhaust gas containing CO are mixed. These exhaust gases are supplied to the NOx catalyst 13a via the exhaust pipe 14.

The exhaust gas containing unburned HC and residual oxygen is:
The air-fuel ratio, that is, the actual average air-fuel ratio is constantly monitored based on the detection signal of the air-fuel ratio sensor 12. And
If the detected value of the air-fuel ratio does not match the above average air-fuel ratio AVAF, supply to some of the cylinders performing the lean combustion operation and / or the remaining cylinders performing the rich combustion operation. The amount of fuel or the amount of air to be applied is appropriately corrected so that the actual average air-fuel ratio matches the average air-fuel ratio AVAF.

Unburned HC supplied to NOx catalyst 13a
Since the NOx catalyst 13a is heated by the heat of the exhaust gas, the NOx catalyst 13a is burned by the presence of the residual oxygen in the NOx catalyst 13a, and the temperature of the NOx catalyst 13a rises rapidly. In this heating mode operation, the average air-fuel ratio AVAF of the exhaust gas is set to 14.7, so that the combustion becomes good, and the NOx catalyst 1 does not increase the pollutants in the exhaust gas.
3a can be heated.

By the way, usually, in the lean combustion operation, the engine output becomes small because the fuel supply amount is small, and in the rich combustion operation, a high output is generated because the fuel supply amount is sufficient. Therefore, when performing the above-described cylinder-by-cylinder air-fuel ratio correction, the selection of the cylinder performing the lean combustion operation and the cylinder performing the rich combustion operation is poor.
If the combustion in the lean combustion operation is continued or the combustion in the rich combustion operation is continued due to the relationship of the ignition order of the cylinders, the engine output becomes uneven, which leads to deterioration of the driving feeling. Therefore, in order to eliminate such inconveniences, the cylinder performing the lean combustion operation and the cylinder performing the rich combustion operation are selected so that the lean combustion operation and the rich combustion operation are alternately performed in a well-balanced manner. You.

For example, when the engine body 1 is a V-type six-cylinder engine as in this embodiment, as shown in the cylinder arrangement diagram of FIG. 8, the ignition sequence of the cylinders is normally # 1- # 2- # 3
Since the order of-# 4- # 5- # 6 is followed, lean combustion operation is performed for the three cylinders # 1, # 3, and # 5 of the left bank 1a, which burn every other, and ## of the right bank 1b. 2, #
For the three cylinders # 4 and # 6, control is performed so as to execute the rich combustion operation.

In the case of an engine body 1 'such as an in-line six-cylinder engine, as shown in the cylinder arrangement diagram of FIG. 9, the ignition sequence of the cylinders is normally # 1- # 5- # 3- # 6- #
2- # 4 or # 1- # 4- # 2- # 6- # 3- # 5
# 1, # 2, # 3 burning every other
Lean combustion operation was carried out for the three cylinders
The three cylinders # 4, # 5, and # 6 may be controlled to perform the rich combustion operation.

The selection of the lean combustion operation cylinder and the rich combustion operation cylinder does not necessarily have to allocate half of the number of cylinders. For example, two of the six cylinders are set to the lean combustion operation and the remaining four cylinders are set to the lean combustion operation. The cylinder may be set to the rich combustion operation. Further, the present invention can be applied not only to the engine body 1 having an even-numbered cylinder such as a six-cylinder engine but also to the engine body 1 having an odd-numbered cylinder such as a five-cylinder engine. And the rich combustion operation cylinder cannot be divided in a well-balanced manner. However, the air-fuel ratio or the like may be adjusted so that the residual oxygen and the unburned HC amount to be exhausted are appropriate.

After performing the air-fuel ratio correction as described above, the process proceeds to step S26. In step S26, the ignition timing is appropriately corrected in accordance with the execution of the air-fuel ratio correction control. In the lean combustion operation, if the ignition timing is advanced to accelerate the combustion, the combustion efficiency can be improved.On the other hand, in the rich combustion operation, if the ignition timing is retarded to retard the combustion, the occurrence of knocking and the like can be reduced. Can be prevented. Therefore, the ignition timing is advanced for a cylinder performing the lean combustion operation, and the ignition timing is delayed for a cylinder performing the rich combustion operation.

Specifically, the ignition timing is advanced based on the following equation (6) for the lean combustion operation, and the ignition timing is retarded based on the following equation (7) for the rich combustion operation. L ignition timing = O / L ignition timing−k × (LAF−O / L target AF) (6) R ignition timing = O / L ignition timing + k × (O / L target AF−RAF) (7) In addition, the L ignition timing indicates the ignition timing of the lean combustion operation,
The ignition timing indicates the ignition timing of the rich combustion operation, and the O / L ignition timing indicates the ignition timing of the normal lean combustion operation.
The L target AF indicates a target air-fuel ratio during normal lean combustion operation, and k is a proportionality constant obtained by an experiment or the like. Note that the above equations are respectively the lean air-fuel ratio LAF described above.
Alternatively, since the rich air-fuel ratio RAF is included, L
Like the LAF and RAF, the ignition timing and the R ignition timing are based on the above-described engine rotation speed Ne and volumetric efficiency ηv.

After the ignition timing has been corrected, the process proceeds to step S28. In step S28, the ISC valve 8
Is adjusted to the valve opening side to correct the intake air amount. The correction of the intake air amount is such that the air-fuel ratio correction control described above reduces the fuel amount for a constant air amount on the lean combustion operation side and decreases the air amount for a constant fuel amount on the rich combustion operation side. In addition, since the output of the engine is reduced as a whole, the present invention is implemented for the purpose of preventing the output reduction. By this correction, the amount of intake air increases, and the engine output can be stably kept constant.

The correction amount of the intake air is set using a map stored in advance based on the engine speed Ne and the volumetric efficiency ηv, similarly to the air-fuel ratio correction amount DAF. When performing the above-described air-fuel ratio correction, ignition timing correction, and intake air amount correction, if these corrections are performed rapidly, the operating state of the engine body 1 may fluctuate. It is desirable to implement as follows.

As described above, when the temperature increase mode operation of the refresh operation is performed, the temperature of the NOx catalyst 13a is rapidly increased, and the temperature TCAT of the NOx catalyst 13a becomes N.
The temperature reaches a predetermined temperature T1 (650 ° C.) which is sufficient to burn and remove the purifying ability reducing substance attached to the Ox catalyst 13a. In the next step S30, the catalyst temperature TCAT detected by the catalyst temperature sensor 26 becomes the predetermined temperature T1.
(For example, 650 ° C.). The determination result is No (negative), and the catalyst temperature TCAT is the predetermined temperature T1 (6
If the temperature is lower than 50 ° C.), it can be determined that the temperature is not yet sufficient to burn and remove the substance having reduced purification ability, and the flow returns to step S16 to wait until the operation state of the engine body 1 is stabilized. On the other hand, if the determination result is Yes (affirmative) and it is determined that the catalyst temperature TCAT has reached the predetermined temperature T1 (650 ° C.), the process proceeds to step S32.

In step S32, the aforementioned step S
The determination result at 16 is Yes (Yes), and it is determined whether or not the elapsed time t at which time measurement was started when the refresh operation was started has passed a predetermined time ts (for example, 5 seconds). If the determination result is No (No) and the predetermined time ts (5 seconds) has not elapsed yet, it can be considered that the operating state of the engine body 1 is unstable, and in this case, the process returns to step S16. Wait until the operation state of the engine body 1 is stabilized. On the other hand, if the determination result is Yes (affirmative), the predetermined time t
When it is determined that s (5 seconds) has elapsed, the operating state of the engine body 1 can be considered to be stable, and the process proceeds to step S34.

Steps S34 to S38 constitute a refresh mode operation of the refresh operation. Here, the temperature of the NOx catalyst 13a which has reached the predetermined temperature T1 (650 ° C.) is determined by the predetermined temperature T1 (6).
50 [deg.] C.), and the substance having reduced purification performance (sulfur and its compounds) is burnt and removed almost completely from the NOx catalyst 13a. In this refresh mode operation, similarly to the above-described temperature increase mode operation, first, the air-fuel ratio is corrected in step S34, then the ignition timing is corrected in step S36, and the intake air amount is corrected in step S38.

First, in step S34, the air-fuel ratio is corrected. Here, unlike the case of the heating mode operation, the average air-fuel ratio AVAF is set to the rich air-fuel ratio, and the value is, for example, 13 .7. And
Using the value of this average air-fuel ratio (13.7),
The lean air-fuel ratio LAF and the rich air-fuel ratio RAF are obtained from (4) and equation (5), and the air-fuel ratio of each cylinder is corrected based on these.

By setting the AVAF to the rich side in this way, the exhaust gas contains more CO and HC than in the heating mode operation. Then, these CO and HC react with the purifying ability reducing substance burned and removed at a high temperature, whereby the purifying ability decreasing substance is satisfactorily released. Since this HC reduces NOx, NOx adsorbed on the NOx catalyst 13a is also removed at the same time.

In step S36, the lean air-fuel ratio LAF and the rich air-fuel ratio RAF corrected and set in step S34 are used to calculate the lean air-fuel ratio from the above-described equations (6) and (7) in the same manner as in the heating mode operation. The L ignition timing of the combustion operation and the R ignition timing of the rich combustion operation are suitably corrected. Then, in step S38, similarly to the case of the temperature rising mode operation, the ISC valve 8 is adjusted to the valve opening side to correct the intake air amount, thereby compensating for a decrease in engine output.

When the refresh mode operation is completed, the process proceeds to step S40, in which a value 1 is set in the flag f (RF) to store that the refresh mode operation has been executed, and the process proceeds to step S42. In step S42,
Every time the step S42 is executed, the accumulated time CST is calculated by the following equation (8), and the catalyst temperature TCAT becomes the predetermined temperature T1.
(650 ° C.) and the continuation time of the refresh operation after a lapse of a fixed time ts (5 seconds) from the start of the refresh operation is integrated.

CST = CST + 1 (8) Since the accumulated time CST is counted up by 1 only when step S42 is executed, the result of the determination in step S16 is No (No).
, Or when either of the determination results in step S30 or S32 is No (No), no addition is made. Therefore, step S16, step S3
The determination results of 0 and step S32 are all Yes (Yes), and only the time when the refresh mode operation is reliably executed is accumulated as the net time. Here, the value 1 to be counted up corresponds to, for example, a reference time Xt set according to the execution cycle of the routine.

The accumulated time CST added in this manner is compared with a predetermined value XC corresponding to a predetermined time t1 (for example, 600 seconds) set in advance by experiments or the like in the next step S44, and the refresh operation is performed. Time t1 (60
(0 seconds). This predetermined time t1 (600 seconds) is a time during which it can be considered that the substance having reduced purification ability has been sufficiently removed. No (No)
If the accumulated time CST has not reached the predetermined value XC,
It can be determined that the removal of the purifying ability reducing substance is not sufficient, and the process returns to step S16 to continue the refresh operation.

When the accumulated time CST has not reached the predetermined value XC and step S16 is executed again, the determination result is Yes (Yes), and the engine main body 1 maintains a favorable operation state for the refresh operation. If so, the process proceeds to step S20. This time, since the refresh mode operation has already been executed and the flag f (RF) has been set to the value 1, the determination result in step S20 is Yes (Yes). In this case, the process proceeds to step S34 without executing the heating mode operation, and only the refresh mode operation is executed to maintain the catalyst temperature TCAT at the predetermined temperature T1 (650 ° C.).

On the other hand, even though the refresh operation is started once, the operation state of the engine body 1 is out of the refresh operation range, and the result of the determination in step S16 is No.
If (No), the refresh operation is stopped, and the process proceeds to step S18. In step S18, the value of the flag f (RF) is reset to zero (f (RF) =
0). Once the value of the flag f (RF) is thus returned to the zero value, the next time step S20 is executed after step S16, the determination result is No (No), and the temperature increase mode operation after step S24 is performed. Will be executed again. As a result, the catalyst temperature TCAT lowered by stopping the refresh operation is reduced again to the predetermined temperature T1 (6).
50 ° C.).

If the result of the determination in step S44 is Yes (affirmative) and it is determined that the accumulated time CST has reached the predetermined value XC, it can be regarded that the substance having reduced purification ability has been almost completely removed, and the refresh Finish driving,
Finally, step S46 is executed. In step S46, upon completion of the refresh operation, the accumulated time CST, the accumulated fuel consumption F, and the value of the flag f (RF), which have been accumulated, are reset to zero values. The 30 damper clutches 40 can be directly connected. This prepares for the next refresh operation.

In the above embodiment, the amount of the substance having a reduced purification capacity is estimated on the basis of the accumulated fuel consumption F. In addition, the running distance D, the intake air accumulation A, the engine body Even when estimation is performed based on the first operation time H, the same effect as in the case of the integrated fuel consumption F can be obtained. In this case, the travel distance D is obtained by the distance meter 25, and the integrated intake air amount A is obtained by calculating the integrated value of the number of vortex pulses of the Karman vortex airflow sensor 6. As for the operating time H, for example, the time during which the engine body 1 is operating may be measured by a timer.

When estimating the adhesion amount of the purification-reducing substance based on the traveling distance D, as shown in FIG. 5, steps S10 and S12 which are the adhesion amount estimating means in the above-described flowchart of the refresh control are performed. Step S100 for calculating the travel distance D and step S120 for determining whether or not the travel distance D has reached a predetermined value D1 (for example, 1000 km) are replaced. Further, instead of resetting the integrated fuel amount F in step S46, the travel distance D is reset to a zero value in step S46.
Replace with 0.

When estimating the adhesion amount of the purification-reducing substance based on the integrated intake air amount A, as shown in FIG. 6, steps S10 and S12 which are the adhesion amount estimation means in the flowchart of the refresh control. Are replaced with step S101 for calculating the integrated amount A of intake air and step S121 for determining whether the integrated amount A of intake air has reached the predetermined value A1. Further, instead of resetting the integrated fuel amount F in step S46, the process is replaced with step S461 in which the integrated intake air amount A is reset to a zero value.

Similarly, in the case of estimation based on the operation time H, as shown in FIG. 7, the adhesion amount estimating means in the flowchart of the refresh control is used to calculate the operation time H in step S102 and the operation time H is set to the predetermined value. H
Step S122 is performed to determine whether or not 1 has been reached. Further, instead of resetting the integrated fuel amount F in step S46, step S462 is performed to reset the operation time H to a zero value.

As described above in detail, the lean combustion and the rich combustion are performed for each cylinder, and the unburned H
The air-fuel ratio correction control is performed so as to simultaneously contain C and oxygen, and the unburned HC is burned in the NOx catalyst 13a.
Since the refresh operation for raising the temperature of the x catalyst 13a is performed, the substance having a reduced purification ability attached to the NOx catalyst 13a is favorably burned and removed from the NOx catalyst 13a by the combustion heat. As a result, the NOx adsorption capacity of the NOx catalyst 13a is regenerated, and the NOx purification efficiency is restored. Also, during this refresh mode operation, H is contained in the exhaust gas passing through the NOx catalyst 13a.
Since C is contained, this HC simultaneously causes N
Ox is also well reduced and removed.

In the above-described embodiment, the determination result of the operation state determination in step S16, the determination of the catalyst temperature in step S30, and the determination of the elapsed time in step S32 are all YES (affirmative). ), The cumulative time CST is counted up only when the refresh operation is performed well. However, the present invention is not limited to this. For example, the operation state determination result in step S16 and the catalyst temperature TCAT in step S30 may be used. The accumulated time CST is counted up when only the result of the determination is Yes (affirmative), or when only the result of the determination at the step S16 and the result of determination of the elapsed time t at the step S32 are Yes (affirmative). Has the same effect. Also,
A sufficient effect can be expected even if the determination is made based only on the determination result of the operation state in step S16.

In the above embodiment, the cycle of the refresh operation is changed every time the purification capacity reducing substance reaches a predetermined amount.
That is, each time the integrated fuel consumption F reaches the predetermined value F1 (the predetermined value D1 for the traveling distance D, the predetermined value A1 for the intake air integrated amount A, and the predetermined value H1 for the operating time H), the NOx catalyst 13a uses As the time becomes longer, the deterioration progresses. Therefore, it is more effective to gradually reduce each predetermined value and shorten the implementation cycle.

Further, in the above embodiment, the engine body 1
Is a V-type six-cylinder engine, but is not limited by the number of cylinders or the engine type (for example, horizontally opposed type), and can be applied to any number of cylinders and any engine type.

[0074]

As is apparent from the above description, according to the exhaust gas purifying catalyst apparatus of the first aspect of the present invention, the nitrogen oxides contained in the exhaust gas during the lean combustion operation are disposed in the exhaust passage of the internal combustion engine. In the exhaust gas purifying catalyst device of the internal combustion engine provided with the exhaust gas purifying catalyst for adsorbing the gas, the adhering amount estimating means estimates the adhering amount of the purifying ability reducing substance adsorbed on the exhaust purifying catalyst and reducing the purifying ability of nitrogen oxides, When the amount of adhesion exceeds a predetermined amount, the temperature of the exhaust purification catalyst is raised by the catalyst heating means, and the purification performance-reducing substance is satisfactorily burned off from the exhaust purification catalyst. The adsorption capacity will be restored, but when the adhesion amount estimating means estimates the adhesion amount of the purification capacity deteriorating substance, the purifying capacity reducing substance Easily in highly during the lean-burn operation of the catalyst deterioration so as to integrate the fuel consumption of internal combustion engines, the adhesion amount of decreased reducing ability substance can be easily and accurately estimated based on the accumulated value of the fuel consumption.

According to the second aspect of the present invention, there is provided an exhaust purification catalyst device provided with an exhaust purification catalyst disposed in an exhaust passage of an internal combustion engine and adsorbing nitrogen oxides in exhaust gas during a lean combustion operation. In the exhaust gas purification catalyst device, the adhesion amount estimating means estimates the adhesion amount of a purification performance reducing substance that is adsorbed by the exhaust purification catalyst and reduces the purification capability of nitrogen oxides, and when the adhesion amount exceeds a predetermined adhesion amount,
Although the temperature of the exhaust purification catalyst is raised by the catalyst heating means, the substances with reduced purification performance are favorably burned and removed from the exhaust purification catalyst, and the ability to adsorb nitrogen oxides on the exhaust purification catalyst is restored. When estimating the adhering amount of the purifying ability lowering substance by the adhering amount estimating means, the consumed fuel amount accumulating means is adapted to accumulate the consumed fuel amount when the purifying ability lowering substance having a catalyst temperature equal to or lower than a predetermined temperature easily adheres. In addition, the amount of the substance having reduced purification ability can be easily and accurately estimated based on the integrated value of the consumed fuel amount.

According to the third aspect of the present invention, the internal combustion engine includes a fuel injector driven by a pulsed current, and the fuel consumption integrating means integrates the driving pulse width of the fuel injector. Since this integrated value is used as the integrated value of the consumed fuel amount, the amount of the substance with reduced purification ability can be easily estimated from the integrated value of the drive pulse width of the fuel injection valve.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an internal combustion engine including an exhaust purification catalyst device to which an embodiment of the present invention is applied.

FIG. 2 is a schematic configuration diagram of a power plant of a vehicle equipped with an internal combustion engine equipped with an exhaust purification catalyst device.

FIG. 3 is a part of a flowchart of a refresh control routine executed by an electronic control unit (ECU) of FIG. 1;

FIG. 4 is the remainder of the flowchart of the refresh control routine following the flowchart shown in FIG. 3;

FIG. 5 is a part of a flowchart of a refresh control routine in a case where the means for estimating the amount of adhered substance having a reduced purification ability is replaced with estimation based on a traveling distance.

FIG. 6 is a part of a flowchart of a refresh control routine in a case where the means for estimating the amount of the substance with reduced purification ability is replaced with estimation based on the integrated amount of intake air.

FIG. 7 is a part of a flowchart of a refresh control routine in a case where the means for estimating the amount of the substance with reduced purification ability is replaced with estimation based on operation time.

8 is a schematic diagram showing a cylinder arrangement of the V-type six-cylinder engine shown in FIG.

FIG. 9 is a schematic diagram showing a cylinder arrangement of an in-line six-cylinder engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 1a One side (left side) bank 1b The other side (right side) bank 3a Fuel injection valve 3b Fuel injection valve 6 Air flow sensor 8 ISC (idle speed control) valve 12 Air-fuel ratio sensor 13 Exhaust purification catalyst 13a NOx catalyst 13b Three way Catalyst 16a Spark plug 16b Spark plug 18 Crank angle sensor 23 Electronic control unit (ECU) 25 Distance meter 26 Catalyst temperature sensor 30 Automatic transmission (AT) 33 Torque converter 40 Damper clutch

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ryo Hirako 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Shogo Omori 5-33-8 Shiba 5-chome, Minato-ku, Tokyo Mitsubishi Inside the Automotive Industry Co., Ltd. (72) Daisuke Mibayashi 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Yoshiaki Kodama 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Inside the Industrial Co., Ltd. (72) Inventor Kazuo Koga 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industrial Co., Ltd.

Claims (3)

[Claims] 1. An exhaust purification catalyst device for an internal combustion engine, comprising: an exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine and adsorbing nitrogen oxides in exhaust gas during a lean combustion operation. An adhesion amount estimating unit for estimating the adhesion amount of the purified purification-reducing substance, and a catalyst heating unit for increasing the temperature of the exhaust gas purification catalyst when the adhesion amount estimated by the adhesion amount estimating unit reaches a predetermined adhesion amount. The adhesion amount estimating means has a consumed fuel amount integrating means for integrating the consumed fuel amount during the lean combustion operation of the internal combustion engine, and the consumed fuel amount integrated value obtained by the consumed fuel amount integrating means is An exhaust purification catalyst device for an internal combustion engine, wherein when a predetermined value is reached, it is estimated that the amount of the substance having reduced purification ability has reached the predetermined amount. 2. An exhaust purification catalyst device for an internal combustion engine, which is provided in an exhaust passage of the internal combustion engine and has an exhaust purification catalyst that adsorbs nitrogen oxides in exhaust gas during a lean combustion operation. An adhesion amount estimating unit for estimating the adhesion amount of the purified purification-reducing substance, and a catalyst heating unit for increasing the temperature of the exhaust gas purification catalyst when the adhesion amount estimated by the adhesion amount estimating unit reaches a predetermined adhesion amount. Wherein the adhesion amount estimating means includes a catalyst temperature detecting means for detecting a temperature of the exhaust gas purification catalyst, and integrates a fuel consumption amount when the temperature detected by the catalyst temperature detecting means is equal to or lower than a predetermined temperature. A fuel consumption amount integrating means, and when the fuel consumption amount integrated value obtained by the fuel consumption amount integrating means has reached a predetermined value, the amount of the substance having a reduced purification capacity becomes the predetermined amount. An exhaust gas purifying catalyst device for an internal combustion engine, which is estimated to have been reached. 3. The internal combustion engine includes a fuel injection valve driven by a pulsed current, and the fuel consumption amount integrating means integrates a driving pulse width of the fuel injection valve, and the integrated value is used as the fuel consumption amount. Characterized in that it is a quantity integrated value,
The exhaust gas purifying catalyst device for an internal combustion engine according to claim 1 or 2.